Proceedings of the International scientific and practical conference ― Cambridge Science and Education Conference‖ (February 23-25, 2026) / Publisher website: www.naukainfo.com. – Cambridge, United Kingdom, 2026. - 289 p.

86 In the case under consideration, the butt connection of the tail section with the fuel tank was carried out using n bolts, which were evenly spaced around the circumference of the frame made of aluminum alloy AMg6, through steel unloading sleeves coaxially screwed into the tank frame. Previously, the value of the maximum operational tensile longitudinal force експ T acting on the joint node, which is realized in the case of LV transportation, was also determined with sufficient accuracy. According to the classical calculation scheme for a flange connection, the calculations also assumed that in a group connection the destructive loads for all bolts would be the same. The determination of the SSS of such a threaded connection was carried out using the finite-element analysis package Nastran. The geometric dimensions and all physical and mechanical characteristics of the connecting elements were considered to be given with the required accuracy. Since the stiffness of the fuel tank frame exceeds the stiffness of the upper end frame of the tail section by more than an order of magnitude, the fuel tank frame was considered to be absolutely rigid in numerical modeling. As a result of the calculations, it was found that the discrepancy between the calculated and destructive experimental data may be due to the incorrect choice of the initial calculation scheme of the bolted connection, due to the failure to take into account in the calculations additional forces caused by the presence of the effect of eccentric tension ("force lever effect"). This is due to the fact that the direction of the axes of all 60 bolts does not coincide with the direction of rotation of the forming shell of the oxidizer tank, which must be taken into account when building the calculation scheme. In this case, the external tensile load has an eccentricity of application equal to the distance between the axes of the bolts and the median surface of the compartment shell, and, as a result, leads to the appearance of additional components of the moment of the applied load. Fig. 2 presents the results of finite-element analysis, demonstrating the essence of the effect of eccentric tension during the deformation of a bolted connection.